File photo. Ingram Publishing/Thinkstock(NORTON SHORES, Mich.) -- A Michigan mother who disappeared while working the late shift at a gas station may have known her abductor, police said Monday.

Jessica Heeringa, 25, was working alone Friday night at a Norton Shores, Mich., Exxon station around the time police believe she was abducted.

"There is no sign of a struggle in the store, so it's possible she knew who the person was as a customer or as an acquaintance," Norton Shores Police Chief Daniel Shaw told ABC News.

Heeringa's purse and keys were found inside the store, he said, and robbery didn't appear to be a motive since the store's cash drawer was left untouched.

Shaw said his team of investigators has fielded tips from around the country. Police are seeking the driver of a gray minivan that was seen in the area at the time of Heeringa's disappearance, he said.

The gas station was not outfitted with security cameras on the night of Heeringa's disappearance, Shaw said, making tips even more crucial.

Jessica's mother, Shelly Heeringa, told ABC News that someone saw her daughter "walk out of the store with this guy like there was no problem," but when they got to his van, a struggle ensued.

On Friday night, Heeringa spoke to her fiance, Dakotah Dyer, between 10 and 10:15 pm and told him she planned to be home early from her shift, he said.

Police said Heeringa's last transaction took place at 10:55 p.m. She was preparing to close the store for the night, but 15 minutes later authorities said they received a call from a concerned customer reporting that there was no employee at the open gas station.

"In 15 minutes that store would've been closed and she would've been on her way home," Shelly Heeringa said.

The family is canvassing the area, putting up fliers and hoping someone comes forward with information that will help bring Jessica home to her 3-year-old son.

"She's a good mother, and she needs to come home," Dyer said. "She has a family that loves her."